This patch fixes an ICE during error-recovery regression in the C front-end.
The symptom is that the middle-end's sanity checking assertions fail during
gimplification when being asked to increment an array, which is non-sense.
The issue is that the C-front end has detected the type mismatch and
reported an error to the user, but hasn't provided any indication of this
to the middle-end, simply passing bogus trees that the optimizers recognize
as invalid.
This appears to be a frequently reported ICE with 94730, 94731, 101036
and 101365 all marked as duplicates.
I believe the correct (polite) fix is to mark the mismatched types as
problematic/dubious in the front-end, when the error is spotted, so that
the middle-end has a heads-up and can be a little more forgiving. This
patch to c-decl.c's duplicate_decls sets (both) mismatched types to
error_mark_node if they are significantly different, and we've issued
an error message. Alas, this is too punitive for FUNCTION_DECLs where
we store return types, parameter lists, parameter types and attributes
in the type, but fortunately the middle-end is already more cautious
about trusting possibly suspect function types.
This fix required one minor change to the testsuite, typedef-var-2.c
where after conflicting type definitions, we now no longer assume that
the (first or) second definition is the correct one. This change only
affects the behaviour after seen_error(), so should be relatively safe.
This patch has been tested on x86_64-pc-linux-gnu with "make bootstrap"
and "make -k check" with no new failures. Ok for mainline?
2020-08-31 Roger Sayle <ro...@nextmovesoftware.com>
gcc/c/ChangeLog
PR c/79412
* c-decl.c (duplicate_decls): On significant mismatches, mark the
types of both (non-function) decls as error_mark_node, so that the
middle-end can see the code is malformed.
(free_attr_access_data): Don't process if the type has been set to
error_mark_node.
gcc/testsuite/ChangeLog
PR c/79412
* gcc.dg/pr79412.c: New test case.
* gcc.dg/typedef-var-2.c: Update expeted errors.
Roger
--
diff --git a/gcc/c/c-decl.c b/gcc/c/c-decl.c
index 221a67f..52fa2ca 100644
--- a/gcc/c/c-decl.c
+++ b/gcc/c/c-decl.c
@@ -2957,6 +2957,17 @@ duplicate_decls (tree newdecl, tree olddecl)
{
/* Avoid `unused variable' and other warnings for OLDDECL. */
suppress_warning (olddecl, OPT_Wunused);
+ /* If the types are completely different, poison them both with
+ error_mark_node. */
+ if (TREE_CODE (TREE_TYPE (newdecl)) != TREE_CODE (TREE_TYPE (olddecl))
+ && olddecl != error_mark_node
+ && seen_error())
+ {
+ if (TREE_CODE (olddecl) != FUNCTION_DECL)
+ TREE_TYPE (olddecl) = error_mark_node;
+ if (TREE_CODE (newdecl) != FUNCTION_DECL)
+ TREE_TYPE (newdecl) = error_mark_node;
+ }
return false;
}
@@ -12209,7 +12220,7 @@ free_attr_access_data ()
attr_access::free_lang_data (attrs);
tree fntype = TREE_TYPE (n->decl);
- if (!fntype)
+ if (!fntype || fntype == error_mark_node)
continue;
tree attrs = TYPE_ATTRIBUTES (fntype);
if (!attrs)
diff --git a/gcc/testsuite/gcc.dg/typedef-var-2.c
b/gcc/testsuite/gcc.dg/typedef-var-2.c
index 716d29c..bc119a0 100644
--- a/gcc/testsuite/gcc.dg/typedef-var-2.c
+++ b/gcc/testsuite/gcc.dg/typedef-var-2.c
@@ -4,12 +4,13 @@
int f (void)
{
extern float v;
-
+/* { dg-message "note: previous declaration" "previous declaration" { target
*-*-* } .-1 } */
return (v > 0.0f);
}
extern int t;
+/* { dg-message "note: previous declaration" "previous declaration" { target
*-*-* } .-1 } */
typedef float t; /* { dg-error "redeclared as different kind of symbol" } */
-t v = 4.5f;
+t v = 4.5f; /* { dg-error "conflicting types" } */
/* { dg-do compile } */
/* { dg-options "-O2" } */
int a;
/* { dg-message "note: previous declaration" "previous declaration" { target
*-*-* } .-1 } */
void fn1 ()
{
a++;
}
int a[] = {2}; /* { dg-error "conflicting types" } */
